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TELECOMMUNICATIONS AND OPTICS IN HISTORICAL ASPECT
Adzhemov Artem Sergeevich,
Ph.D., Professor, Moscow Technical University
of Communication and Informatics, Moscow, Russia, mtuci@mtuci.ru
Keywords: fiber-optic, history of telecommunications,
Khromoy Boris Petrovich,
Ph.D., Professor, Moscow Technical University
of Communication and Informatics, Moscow, Russia
Wide application of fiber-optic communication systems is considered a major achievement of science and technology over the past decade. The same time it is believed that the historical aspect is a natural process of development of communication, because for a century mankind has mastered all of the higher frequency band of radio waves, and finally mastered the optical range. In fact, the history of communication covers a much larger period of time, and its beginning is connected with the optical range. Development of television equipment gave impetus to the development of electron optics. Electron optics - the branch of physics that studies the laws of propagation of beams of charged particles - electrons and ions - in magnetic and electric fields and issues of focus, tilt, and imaging. The development of electron optics began with the study of cathode rays by means of which was obtained shadow image of the object, indicate that the nature of their distribution is similar to the propagation of light beams in geometrical optics. Image shift caused by a magnetic field showed that the cathode rays are a stream of charged particles
Electron optics together with the use of an electric field also uses the magnetic field. Widely used device which bears the name of the magnetic lens. The magnetic lens is typically a solenoid with a strong magnetic field, coaxial with the electron beam. In order to concentrate the magnetic field on the axis of symmetry, the solenoid is placed in a steel casing with a narrow inner annular slit. If a divergent beam of charged particles falls in a uniform magnetic field, directed along the beam axis, the velocity of each particle can be decomposed into two components: the transverse and longitudinal. In summary, it can be concluded that the combination of scientific advances optical communications and has revolutionized the modern system of information communications.
Для цитирования:
Аджемов А.С., Хромой Б.П. Электросвязь и оптика в историческом плане // T-Comm: Телекоммуникации и транспорт. - 2016. - Том 10. - №2. - С. 71-79.
For citation:
Adzhemov A.S., Khromoy B.P. Telecommunications and optics in historical aspect. T-Comm. 2016. Vol. 10. No.2, рр. 71-79. (in Russian).
The oldest and most common mode of transmission of information to almost the first half of the XIX century was the way, based on the use of light signals. Also used special devices with moving parts, the different relative positions of which were symbols. But the symbols were perceived at a distance the human eye and, therefore, transferred to the light range.
In accordance with the modern terminology these ancient devices can be called "optical telegraph". The ancient optical telegraph - it fires, torches, semaphores. One of the oldest types of such means of communication describes the ancient Greek military commander and scientist Polybius (201-120 gg. BC.E.), in his "General History". The ancient Greek poet Aeschylus (525-456 gg. BC. E.) in his tragedy "Agamemnon" describes how many centuries BC, with the help of the fires through a series of waypoints it was transferred to the news from Asia Minor in the Mycenaean castle of the capture of the Greeks of the legendary Troy. In Russia, in the ancient times it was also used to signal fires, which are reported, for example, about the invasion of the enemy.
In the historical literature suggests that the Tower of Babel could be used for Optical telegraphy. The Chinese for the same purpose were lit bright lights on towers located along the Great Wall of China. This method of transmission of news through the lights, and later used in the majority of savage peoples, especially in Africa.
Much later it becomes more perfect telegraphs where symbols are not transmitted by means of light sources and beams, sent from one place to another and through special arrangements with moving parts in the form of lines or circles that are visible from a distance. The first inventor of the optical telegraph of this kind is considered to be a well-known English scientist Robert Hooke, who not only invented, but also built a signaling device, which was demonstrated in their 1684. Then the Frenchman G. Amontons in 1702 arranged for the optical telegraph with movable slats, which he showed in action at the court.
In the XVIII century, the optical telegraph used very intensively. In 1778, to establish communications between the Paris and Greenwich Observatory was arranged optical telegraph that used lights. A variation of the optical telegraph in XIX appeared "helio", which was widely used in the military. The main part of the heliograph was a mirror through which light beams were directed to a place where there was another such mirror. Symbols formed a short turn mirrors into one or the other side. Under favorable weather conditions such signs could be transmitted to a distance of 65 km. At night, in the moonlight, this distance is reduced to 15 km, and the illuminated lamps up to 5 km.
The simplicity of the device and installation, lightness, cheapness heliographs mirror, made their use feasible for military purposes. Is used in the army, mainly in the military courts, and more sophisticated signaling devices with strong electric lights - spotlights. To direct rays voltaic arc parallel beam used in them and spherical or parabolic mirrors and a variety of glass lenses. The improvement spotlights attended S. Mangin, P. Lemone, V.N.Chikolev, V. Siemens and particularly J. Schuckert.
Optichesky Telegraph - as the fastest means of communication even at the end of the XIX century, was invented in 1780 in France, Claude Chappe. But in 1792, the instrument was improved K. Sharpe and his brother, and was presented to the National Convention they called semaphore (vector characters).
The first line of the system was built in I 794 and connecting Paris and Lille. The first notice on it has been received on September I of the capture of the French on the same day in the morning city Conde Austrians. Over 225 km were built 22 stations. For transmission of one sign thus required 2 minutes. Soon there were others built the line, and the system Chappe brothers wide use. His military victories Napoleon I obliged many optical telegraph, by which he was able to quickly transfer their orders for long distances.
Despite the shortcomings of optical telegraphy, which consist mainly in its dependence on the weather, it is actively used almost to the middle of the XIX century in Russia -before the start of the 1860s,
In Spain, the first in the line of optical telegraph was built in 1798 the Spaniard A. Betancourt. She has joined Cadiz and Madrid. Betancourt has used its own system of optical communication, later recognized the best in Europe. Later A. Betancourt moved to Russia and was a prominent Russian statesman and scholar, lieutenant-general in the Russian service, an architect, a builder, a mechanical engineer and organizer of the transport system of the Russian Empire.
In the Russian Empire l.P. Kulibin in 1794 was invented and built «dalneizveschayuschaya Machine" is an optical semaphore in which he, in addition to mirrors, used a lantern they invented a reflecting mirror. This allows you to build intermediate stations at greater distances and use the telegraph, and day and night, even in a small fog. Frame semaphore Kulibin was used T-French, but it was invented by an ingenious drive mechanism to move the frame, and a new simplified code. Kulibin code tabulated by which accelerated the transfer and decoding of signals, Kulibin invention had the effect, but the money for the construction of telegraph lines in the Academy of Sciences has not been. After the demonstration, the machine Kulibin was deposited in a museum.
In 1824, it was built Russia's first line of optical telegraph between St. Petersburg and Shlisselburg on which transmitted information on the navigation on the Neva River and Lake Ladoga. It was based system A. Betancourt, received by the time the big distribution.
The development of optical communication in St. Petersburg was very slow: only in 1833 was opened on the second line of Petersburg - Kronstadt, which went through Strelna and Oranienbaum. By 1835 this line were added two more; St, Petersburg - Tsarskoye Selo and St. Petersburg -Gatchina. Nicholas I could without of his working cabinet, to give orders to the fleet using the telegraph, which he put into action. This is described in detail in the book of Custine "Russia in 1839".
In the reign of Nicholas I, it was created by a special committee in the Ministry of War to consider the proposed for use in the Russian optical telegraph. From 1827 to 1833
The Committee considered a number of projects of Russian and foreign inventors: Captain - Lieutenant Chistyakov, merchant Schegorina, General Karbonera, Ferrier, Leroux, Tone!, Chateau, Ganon, and others. For buildings in Russia have chosen the optical telegraph, developed by a former employee Karl Shappo engineer Jacques Chateau. In Russia, he was called Peter. The design of its telegraph was much simpler than that of C. Chappe.
Chateau has developed not only the construction of the telegraph, and the codebook for the compilation of messages, as well as the "Regulation on the Kronstadt telegraphic lines", "Charter telegraphic Signalist." The Charter was published in St. Petersburg in the military printing house in 1835.
The world's longest line optical telegraph Petersburg (Winter Palace) - Warsaw was built in the years 1835-1838 and was inaugurated December 20, 1839. The nearest station of the Winter Palace was the place of modern metro station "Institute of Technology". The length of the lines was 1200 km, it served 1904 man. To transmit signals used by 149 towers built by "His Majesty the approved" pattern and having a height of 21.5 m. The message from the Winter Palace in Warsaw came to an average of 20 minutes. To prepare telegraph serving line optical telegraph in 1840 opened a "constant signal school."
Original station in St. Petersburg, located in a small hexagonal turret topped with gilded ball and situated on the western fa3ade of the Winter Palace. The tower was built by the architect LI Charlemagne in 1835 and was intended to contain the optical (semaphore) telegraph.
Prior to her almost at the same place, but at the corner of the palace, overlooking the Neva River, was a wooden "telegraphic house" with a gable roof, where he worked first optical telegraph in 1833. From this "house" ran a telegraph line connecting St. Petersburg to Kronstadt,
Optical telegraph couid use ordinary citizens. You could send a "optical" telegram to Gatchina or Vilna - they took in the "telegraphic house" in the tower of the City Council. But as soon as it is quite expensive, and the popularity of the townspeople this type of communication is not received. In addition, it is strongly dependent on the weather.
In the library of the Central Museum of Communications Popov, founded as a telegraph museum in 1872 at the initiative of the director of the Telegraph Department Charles Luders are telegraphic Signalist Charter, Writer Peter Chateau and Concise Dictionary for Kronstadt telegraphic line 1837. These documents can form a complete picture of how to create and extend the telegraph line of message. At intermediate towers - stations in a special "Signalist" recorded all received and transmitted signals further with the time of transmission and its family. The contents of the message he did not know. It should be noted that the Central Museum of Communications Popov - one of the oldest science and technology museums in the world.
The optical telegraph quickly gained popularity. In the first quarter of the XIX century there were semaphore telegraph line in many European countries and in America, Algeria, Egypt and India. It is a vivid description of the optical tele-
graph left us in the novel by Alexandre Dumas' The Count of Monte Cristo."
Optical Telegraph lost its relevance in the early 1850s, with the introduction of the electric telegraph. In Russia in 1852, it was built by the electric telegraph line between St. Petersburg and Moscow, while the optical telegraph line Petersburg - Warsaw for some time continued to operate. In 1854, the Russian optical telegraph ceased to exist.
Despite the introduction of the electric telegraph, optical telegraph remained popular in the Navy. Optical semaphore Navy was one of the most basic forms of communication between ships. At the end of the XIX and early XX century, with the advent of autonomous power in the optical telegraph began to use electric lights, which made it possible to develop a light alphabet.
Optical semaphore at the end of the XIX century and has been applied on the railway. Railway semaphore alphabet at first was not very complicated, but over the years the need for it grew and led to the development of its own system of light signals.
Saving optical methods for transmitting signals in the fleet and rail due to the fact that in these areas there was no opportunity to transmit electrical signals through the wires.
It should be noted another important property of optical method of information transfer - the ability to receive the signal visually. It is in some cases is important, even if the original information is transmitted over the wire. With the development of road transport there was a kind of simplified optical semaphore - a traffic light.
The loss of relevance of the optical telegraph in 1854 in Russia had a good reason. In 1800, an Italian scientist, physicist, chemist and physiologist Alessandro Volta created the world's first chemical current source "Voltaic pile." Starting from 1800, it became possible to produce electricity through chemical reactions. This invention has had a tremendous impact not only on the development of the science of electricity, but also in the entire history of human civilization.
After the invention of the electrochemical A. Volta took only two years and in 1802 Vasily Vladimirovich Petrov (1761-1834) - Russian experimental physicist, electrical engineer, academician of the Petersburg Academy of Sciences created a current source "Voltaic pile" with electromotive force of about 1700 V. In 1803, Vladimir Petrov published the book "Proceedings of Galvani - volt experiments which describes a method for the manufacture of the voltaic pile, the phenomenon of the electric arc and the possibility of its application to lighting, electric welding and electric brazing metal.
It is obvious that the invention of the electrochemical cell was of paramount importance. Until then studied fixed electric charges, i.e. there was only electrostatics. With the receipt of the current began to develop electrodynamics. In the experiment, Oersted accidentally discovered the effect of the current flowing through the meta! wire in the position of a magnetic compass. Before that, it was believed that the electrical and magnetic phenomena are completely independent.
The phenomenon discovered by Oersted interested in the English scientist Michael Faraday, Having started work in
this direction in 1822, it is only in 1831, found a solution to the problem, discovering eiectromagnetic induction. Already in 1832, for the discovery of Faraday induction was awarded the Copley Medal. In 1845 Michael Faraday introduced the concept of "electromagnetic field".
Scientific achievements Faraday aroused great interest in the scientific world. Already in 183 I, the American scientist Joseph Henry established for Yale College large electromagnet with a pull of 1,000 kg (at the present time it is stored in the Smithsonian Institution in Washington, DC).The properties of the electromagnet, as a mechanical Executive the device, led to the idea of constructing the electromagnetic telegraph.
At December 14, 1846 a young German scientist Ernst Werner von Siemens (1816-1892) in a letter informs the relatives: "I am now almost decided to elect a permanent career in the Telegraph ... Telegraphy become self-important an industry equipment, and I feel called upon to play a role organizer".
October 1, 1847, Siemens together with the mechanic Halske founded by telegraph - construction firm Telegraphenbauanstalt Siemens & Halske (S & H). In 1849 the firm S & H built the first telegraph line in Germany Berlin -Fran kfu rt-on- Main.
Siemens also improved Telegraph arrow Wheatstone-Cooke, for which the First Internationa! Industrial Exhibition in England (1851) was awarded one of the highest awards.
Since 1853 the Firm S & H perform construction of several telegraph lines in Russia, connect Saint-Petersburg to Kronstadt, Helsingfors, Warsaw, Riga, Revel, and took over their maintenance.
It should be noted that on build the constructing the electromagnetic telegraph worked successfully in Russia B.S. Jacobi. !n 1839 he invented the electromagnetic telegraph transmission with the fixation of the text, in 1842 invented the electromagnetic telegraph an arrow, in 1850 the world's first direct-printing the electromagnetic telegraph. In 1843 BS Jacobi built a telegraph line length of 25 km between St. Petersburg and Tsarskoye Selo.
The rapid development of a new type of telegraphy was caused by the significant advantages of the electric telegraph to the optical. These include high-speed signal transmission, no intermediate stations served by the ability to record and transmit information.There was also another reason for the intensive construction of the electric telegraph lines. Important task in those days, was navigation and mapping. The solution of these problems with a high accuracy provide the safety and efficiency of Maritime navigation, as well as the efficiency of the extended building of long roads and canals. The main problem in this case was the problem of determining longitude certain point of the Earth's surface.
As is known, the coordinates of the earth's surface is determined by the latitude (parallels) and the longitude (meridian). The measurement of latitude was carried out using a "sextant". This high-precision measuring instrument used to measure the angle of the sun above the horizon at solar noon. Knowing the date of measurement and the angle can be calculated latitude. The sextant is an optical device, de-
signed as a result of years of work of dozens of scientists and inventors working in different countries. Among them, Jean Picard, Tycho Brahe, Edmunt Halley, Robert Hooke and others.
Not so with the measurement of longitude location. Longitude - angle between the plane of the meridian passing through a given point, and the plane of the initial zero meridian from which counting is carried out longitude. Selection of the zero meridian is arbitrary and depends on the agreement.Currently, the prime meridian is the Greenwich meridian that runs through Greenwich Observatory in south-east London, As previously chosen the zero meridian observatories of Paris, Cadiz, Pulkovo.
To determine the longitude is necessary to determine the time of sunrise in the area compared to the same time at the prime meridian. This required precision clock (chronometer), with a daily error less than 0.5 seconds. Creator of the first accurate clocks are considered to be the two great scientists - Galileo Galilei and Christiaan Huygens. However, that pendulum clocks were not suitable for marine navigation because of the pitching. In 1674 Huygens refused the use of the pendulum clock to sea, and proposed as a regulator of clock oscillating system balance-spiral. And only in 1759 the sea is very high precision clock (chronometer) created the English master John Harrison.
Later, it was started the production of chronometers and their installation on marine vessels. However, a very serious problem remained the initial installation time according to the time of the Greenwich meridian. This problem was solved with the help of telegraph lines in which time signals transmitted to the seaports. At some point, shots were fired from a gun and ships chronometers corrected readings. Traditionally and currently in St. Petersburg takes a shot from a gun in 12 hours. Thus, the electric telegraph, unlike optical, performed a very important function.
By these reasons, the electric telegraph in the mid XVIII century replaced the optic telegraph and the end of the century communications and optics existed separately. However, at the end of the XVIII century the situation changed. In the period from 1885 to 1889 H. Herz performed his famous experiments on the propagation of electrical power, to prove the reality of electromagnetic waves.
In 1887, he published the first article of the experiments "On very rapid electric vibrations," and in 1888 - even more fundamental work "On electrodynamic waves in the air and their reflection, "The main conclusions of Hertz: You can transfer energy to the electric and magnetic fields without wires, fair Maxwell's theory Maxwell's theory is valid, that the speed of propagation of radio waves is equal to the speed of light. Hertz managed not only detect the wave, including, and standing, but also to investigate the speed of their propagation, reflection, refraction, and even polarization.
It should also be noted that in the years 1886-87 Hertz first observed and gave a description of the external photoelectric effect. Thus, the discovery of electromagnetic waves by Hertz served as the basis for the realization of radio and
external photoelectric effect for the Implementation of television.
Later, however, in the implementation of a radio played an important role Tesla. He originated the idea of a transition from DC to change to address energy problems. Tesla experimented not only with high voltage electricity, but gradually increases its frequency.
In 1891, Tesla during a public lecture described and illustrated the principles of radio communication, and in 1893 created a mast antenna for wireless radio. In 1893 Tesla constructed the world's first wave radio transmitter (the primacy of Tesla in the invention of radio has been proven and recognized in 1943 by the US Supreme Court).
In Russia, the radio was invented independently by A. Popov. 18 December 1897 he transmitted by means of telegraph apparatus, connected with the his device, the words "Heinrich Hertz", which are among the first passed by radio. This was expressed in respect of Russian scientist to the scientific achievements of the great scientist. In addition it should be noted the emergence of wireless.
Among the inventors of radio is often called the Italian Marconi. His leadership in the invention of radio is often disputed, but one of his discovery is of interest. In I 90 I he organized the transfer of a radio signal from Europe to America, which experts predict was to give a negative result, since electromagnetic waves travel in straight lines. However, the result was positive. Thus, it was experimentally proved that the "long" electromagnetic waves bend around the Earth's surface and, consequently, there is a phenomenon analogous to the well-known in optics, called diffraction.
While the relationship between the laws of propagation of electromagnetic waves and the laws of optics was not all clear. When mastered a range of short waves, it is allocated to radio amateurs because the experts considered that he was not promising, since short waves travel in straight lines and will go beyond the earth's atmosphere. However, the experience of radio amateurs showed that the waves under certain conditions, have the ability, reflected from the ionosphere to return to Earth, i.e. there is a well-known phenomenon in the optical reflection. Also appeared in demand optical term "refraction."
If we look at the terminology used in the theory of propagation of radio waves and compare it with the terminology used in optics it is possible to identify a lot in common. Thus, for example, uses the principle of Huygens - Fresnel - the basic postulate of the wave theory, which describes and explains the mechanism of propagation of radio waves and light. The principle of Huygens - Fresnel formulated as follows: each element of the wavefront can be considered as the center of the secondary disturbance that generates the secondary spherical waves, and the resulting light field in every point in space is determined by the interference of these waves.
Uses the term Diffraction - bending of waves of obstacles encountered in their way; dispersion - the dependence of the velocity of propagation of monochromatic radiation in the environment, the frequency of this radiation; interference, coherence and other. The coincidence of the above terms
shows that the rapid development of radio engineering in the twentieth century In the theory of propagation of electromagnetic waves great importance have had scientific achievements in the field of optics accumulated in the seventeenth and eighteenth centuries.
In the future the impact of scientific advances in optics on the development of communication technology is clearly evident in the development of color television. To solve this problem, use the scientific results obtained by D. Maxwell, Color theory originates in the work of Isaac Newton, who adhered to the idea of the seven basic colors. Maxwell acted as the continuer of the theory of Thomas Young, proposed the idea of the three primary colors and associate them with the physiological processes in the human body. Important information contained testimonies of patients color blindness, or color blindness. In experiments on color mixing, largely independently repeat the experience of Hermann Helmholtz, Maxwell applied the "top color" drive which was divided into differently colored sectors, as well as the "color box" - to develop his own optical system.
For a graphical representation of colors, the Maxwell, following Jung, used the triangle, inside which the point represent the result of mixing primary colors located at the vertices of the shape. Full mathematical theory of the color of the body created by the Soviet scientist N.D. Nyberg and partly by the German scientist R. Luther. Nyberg book "Theoretical Foundations of color reproduction," published in 1948 became fundamental to the theory and practice of color reproduction. In the international literature there is the term "body color Luther - Nyberg." Thus, the beginning of the development of color television equipment have been developed the scientific foundations of colorimetry.
Development of television equipment gave impetus to the development of electron optics. Electron optics - the branch of physics that studies the laws of propagation of beams of charged particles - electrons and ions - in magnetic and electric fields and issues of focus, tilt, and imaging. The development of electron optics began with the study of cathode rays by means of which was obtained shadow image of the object, indicate that the nature of their distribution is similar to the propagation of light beams in geometrical optics. Image shift caused by a magnetic field showed that the cathode rays are a stream of charged particles
Experiments on the deflection of charged particles combined electric and magnetic fields in 1897 led to the discovery of the electron (J. J, Thompson). One of the first cathode ray tube became oscillographic electron-tube (CRT), invented by Karl F. Brown in 1897. In the improvement of improving the CRT has been carried out focusing the electron beam by a magnetic field coil with current. Theoretical and experimental studies of the motion of electrons in an axisymmetric magnetic field coil current shown that it is suitable for the formation of the electron-optical imaging and, consequently, is an electronic lens.
The relationship of light and electron optics confirms Fig.I, which is considered the principle of focusing the electron beam by means of a system consisting of two anodes.
r rC f : 'I *! *)
Ai
6'
A}
Fig. I
Bb' line (Fig. I) divides the field between the anodes into two parts. The left side of the field enters a divergent electron beam that is focused and in the right part of the field is the dispersion of the flow. The scattering effect is weaker than a focusing because the speed of the electrons in the right part of the field is higher than the left. All field like an optical system consisting of collecting and diffusing lens (lb). Because for several decades black-and-white and color kinescopes were the only devices imaging in TV, they produced tens of millions of units per year.
Electron optics together with the use of an electric field also uses the magnetic field. Widely used device which bears the name of the magnetic lens. The magnetic lens is typically a solenoid with a strong magnetic field, coaxial with the electron beam. In order to concentrate the magnetic field on the axis of symmetry, the solenoid is placed in a steel casing with a narrow inner annular slit. !f a divergent beam of charged particles falls in a uniform magnetic field, directed along the beam axis, the velocity of each particle can be decomposed into two components: the transverse and longitudinal.
The first of these creates a uniform circular motion in a plane perpendicular to the field direction, the second - uniform linear motion along the field. For electrons emitted at different angles, the normal component of the velocity wilt be different, i.e., will be different and they describe the radius of the spirals. The resulting motion of the particle will occur on the spiral, the axis of which coincides with the field direction. However, the ratio of the velocity components normal to the radii of the spirals for the period of rotation will be for all electrons equally; therefore, after one revolution all the electrons will focus at the same point on the axis of the magnetic lens. Thus, with respect to the magnetic field In the electron optics also used the terms "lens" and "axis".
It follows from the above, in communication to the middle of the twentieth century, widely used theoretical foundations of optics. The introduction of television led to the
practical use of optics and contributed to the development of a new section - electron optics. But for more than a century, from about 1850, when most countries ceased to exist optical telegraph, until 1970, the light energy is not used to transmit information in communication networks.
The turning point in the history of communication occurred as a result of the invention of the laser. The word "laser" is made up of the Initial letters of the phrase in the English Light Amplification by Stimulated Emission of Radiation. The invention of the laser associated with the works of Russian scientists Basov and Prokhorov, who in 1958 invented the laser, for which he received the Nobel Prize in 1964, together with the American Townes, whose works are used in the development of Prokhorov. But the Americans have made the first ruby laser and establish serial production, so they are often called the inventor of the first laser. The world's first working laser was constructed by Theodore Maiman in I960. Maiman used ruby rod with pulsed pumping, which gave a red light with a wavelength of 694 nanometers. In 1962 it was created by a semiconductor laser and a photodiode, i.e. It was created compact source and destination of the optical signal.
Creating a small source and receiver optical signal made it possible to use optical fiber for the construction of fiber optic communication lines (FOCL). However, the widespread transition to fiber-optic technology interfere with high attenuation in the optical fiber, so the competition with copper lines was impossible.
Only in 1970 the company Corning Glass (USA), specializing in product development of optical physics of specialized glass over a hundred sixty years, managed to establish commercial production of fiber with low attenuation - 20 dB/km (wavelength 0,85mk) a couple of years — to 4 dB/km. Multimode fiber is passed through it, and several modes of light. By 1983, he mastered the production of single-mode fibers, which passed one mode.
Almost at the same time, Russia and the United States have developed principles of semiconductor lasers based on heterostructures with satisfactory characteristics for the creation of FOCLS. In 1970, on the basis of these developments it was created the first layout of fiber-optic line that can transmit data at a speed of 2 Mbit/s at a distance of 3 km.
In Russia, the first model capable fiber-optic transmit information at speeds hundreds of Mbit/s was established in 1977. In 1981, on the basis of a single-mode optical fiber with losses of less than I DB/km fiber optic link was created layout that provides information transfer at speeds of up to 2 GB/s a distance of 40 km. During these years, it mastered the production of fiber-optic cable on the market when the respective optical sources, photo detectors, and other elements of the light guide technology.
Currently, fiber-optic communication is central to the world of telecommunications.
Already all continents of the world interconnected fiberoptic communication lines. In 2000, the world was laid 90 million kilometers of optical fiber and this number is increasing.
Speed of information transmission over a single fiber is achieved in recent years to 1000 Gb/s. Without modern fiber optic connection it is currently unable to work the Internet. Thus, after almost 150 years of optical communication was again!
It is interesting technical features fiber-optic components, which determine the possibility of an optical network. Of course, the main component is an optical fiber. The invention of the optical fiber and its improvement, led to the creation of a new branch of optics cailed "fiber optics". Theory of fiber optics developed sequentially, due to the gradual improvement of the optical fiber, reduction of the diameter and production of multimode and singlemode fibers.
The outer diameter of all optical fibers of the optical fibers used in the fiber-optic line, standardized and is not protective and strengthening membrane (125 ± I) mm. The diameter of the light-guiding core multimode fiber is 50 microns in European standards and 62,5mkm in the North American and Japanese standards. The diameter of the lightguiding core single mode fibers depending on the type of fiber may be in the range (7-10) mkm. Due to the small diameter of the core of the optical radiation propagates through the fiber in the same (basic, fundamental) mode and as a result, there is no intermode dispersion. Due to the large core diameter multimode fiber propagates a few radiation modes - each at a different angle, and pulse of light feels dispersion distortion.
Multimode fibers are divided into step and gradient. In step refractive index of the fiber cladding to the core changes abruptly. The gradient fibers this change occurs differently - refraction index of the core gradually increases from the edges to the center. This leads to the phenomenon of refraction in the core, thereby reducing the effect of dispersion on distortion of an optical pulse. Gradient refractive index profile of the fiber can be parabolic, triangular, broken and so on.
The gradual improvement of optical communication systems was based on scientific research, the measurement of various parameters and characteristics. This led to the development of a number of new instruments and improvement of the standard base. As an example, such features as the chromatic and polarization - mode dispersion
Chromatic dispersion is the sum of material and waveguide dispersion. Chromatic dispersion occurs due to the fact that the propagation velocity varies with the wavelength. In a homogeneous medium wave propagation velocity can be changed only because of the dependence of the refractive index of the medium wavelength, which leads to the appearance of the material dispersion. The fiber wave propagates in two environments - partially in the core and in part - of the quartz envelope and it takes a certain refractive index average value between the value of the refractive index of the core and quartz sheath .
This average refractive index can be changed for two reasons. Firstly, due to the fact that the refractive indices of the core and silica cladding depends on the wavelength (approximately equal). This dependence leads to material dispersion. Secondly, because when the wavelength varies the depth of
penetration of the field into the quartz sheath and accordingly varies the average value of the refractive index. This is purely a waveguide effect, and therefore there is because it is called the waveguide dispersion.
To date, a number of leading international metrology institutes (METAS - Switzerland, NIST - the US, NPL - UK, CSIC - Spain, HUT - Finland) created a reference apparatus for measuring CD, developed international standards on the measurement of the magnitude and conducted international comparisons.
In Russia, developed and approved by the State primary special standard unit of chromatic dispersion in the optical fiber GET 184-2010, provides playback, storage and transmission unit of the chromatic dispersion. This standard has allowed to provide traceability of the chromatic dispersion in the country in the wavefength 1260 h 1650 nm. The range of measurement of the chromatic dispersion of -400 h + 400 ps / nm with an accuracy of 0.36%.
Another important characteristic of the optical fiber is a polarization mode dispersion (PMD). Under PMD understood averaged in the working spectral range of the differential group delay between orthogonally polarized modes propagating along the fiber cable, and arising from the breach of the concentricity of the core of the optical fiber, the internal and external stresses, inhomogeneity of the material, etc. The occurrence of this delay causes a broadening of the optical pulse is transmitted through the optical fiber, which in turn leads to an increase in the number of bit errors and reduced data rate. Education PMD in an optical fiber is illustrated in Fig. 2 a and b.
_
The quick component
The slow component
Fig.2
► -4
PMD
In an ideal form of fibers (2a) orthogonally polarized waves travel at the same speed. At a deviation from the ideal form of fibers (Fig. 2b) a timing offset indicated as PMD.
Limit allowed in PMD link determines the data rate. It is believed that the maximum possible PMD line should not exceed 10% of the bit time — the time allotted to transmit one bit of data. For example, the network STM-4 data transfer speed 1244.16 Mb/s bit time 803.76 ps and the PMD limit is 80 ps, and the network STM-256 baud rate 39.813 Gbit I s and bit time 25.12 ps and time limit PMD of 10 ps.
St follows that the importance of measuring the PMD increases in accordance with increase in transmission speed. Since the transmission speed is the current trend, there was the task of ensuring metrological maintenance PMD measurement. For the efficient operation of instruments measuring PMD in the Russian Federation was established State primary special standard (GPSE) units of PMD in optical fiber GET 185-2010. This standard provides reproduction of PMD in the 1310, 1550 nm, the amount of PMD in the range of 5-120 ps with an accuracy of 0.005 ps
In this way, the problem to be solved in communication technology, are currently the driving force behind the development of certain areas of optics, both in theory and practice. On the other hand it is of interest to evaluate the progress made in the communications technology development by the optical range.
Fiber-optic lines have a number of advantages over the wire (copper) and radio relay link;
- Low signal attenuation {in some types of fibers of 0.15 dB / km) makes it possible to transmit information at a much greater distance without using amplifiers. Amplifiers can be placed in a fiber optic link 40, 80 and 120 kilometers, depending on the class of terminal equipment;
- High-bandwidth optical fiber can transmit information at high speed, unattainable for other communication systems;
- High reliability of the optical medium: optical fibers do not oxidize, do not get wet, they are not subject to electromagnetic interference;
- Information security - information on the optical fiber is passed "from point to point." Connect to the fiber and read the transmitted information without damaging it is almost impossible;
- Highly protected from interfiber influences - the level of radiation shielding more than 100 dB. Radiation of a single fiber does not affect the signal in the adjacent fibers;
- Small size and weight.
Comparative evaluation of fiber-optic lines may be formed by Fig. 3, which shows graphs depicting baud rate (bits/s) at different times in telephone lines, coaxial lines and advanced in a fiber-optic wavelength division multiplexing.
Speed (ransmilioas bps
10" 10'° 10" 10> 101 103 10" 10'
Fiber-optic Hues with spectral seal
— Modern coaxial line
Telephone line
J_I_I_L
JL
1880 1900 1920 1940 I960 1980 2000 Year
Fig. 3
From Fig. 3 shows that in 90 years the performance communication lines increased by five orders of magnitude,
from the first telephone lines, data transfer rate which was I bit/s. Approximately the same growth was recorded, and in the last 20 years - the rate reached about i.6 Tbit/s, The scale of the development of fiber-optic communication is really striking. World production of optical fibers currently stands at 60 million. Km / year, i.e. every minute in communication systems are laid over 100 km of optical cables. All the continents are linked by underwater fiber-optic cables.
The rapid growth rate information associated with the fiber-optic wavelength division multiplexing. Based on this technology was laid in 1958, before the advent of the fiber optics. But it took about 20 years before it created the first system components, called multiplex.
Originally, they were designed for laboratory research, and only in 1980, the technology WDM (Wavelength Division Multiplexing, WDM) has been proposed for telecommunications. And in five years, the research center of the company AT & T has implemented technology of dense wavelength division multiplexing (Dense Wavelength Division Multiplexing, DWDM ), when it was possible to create a single optical fiber 10 channels at 2 Gb / c.
Frequency plan for DWDM systems is determined by the standard of the International Telecommunication Union (International Telecommunication Union, abbreviated as ITU) -ITU G.694.1. According to ITU in DWDM systems use "C" (1525... I565nm) and "L" (1565... I625nm) fiber transparency window. In each band fall to 80 channels with a pitch 0.8nm (100 GHz). Normally only "C" range, since the number of channels that can be arranged in this range so lacking in abundance, besides attenuation of G.652 standard C-band somewhat lower than in the L-band.
To coordinate operation of the various sections of the telecommunications network it becomes necessary to convert the frequency of the transmitted signals, as the various parts may be transmitted at different wavelengths. All components of DWDM-systems running on standardized frequencies of the frequency plan of ITU-T. To convert an optical input signal into DWDM - the system at the desired ITU-frequency-use DWDM transmitters. To convert the respective optical signal (prior to entering a DWDM-system, its frequency is not included in the frequency grid ITU-T) is used DWDM-transponders (or frequency adapters).
Finally, if in DWDM-system frequency one-DWDM devices do not coincide with the frequencies of the other (in this case all the frequencies included in the keeper ITU-T), for harmonization of these devices using wave converters.
In table I shows the parameters of the three channels in a grid-DWDM channel in accordance with ITU C-band with 100 GHz increments.
Table I
Channel Frequency THz Wavelength nm Channel Frequent/ THi Wavelength nm
17 191.7 1563,86 40 194,0 ! 545,32
18 191,8 1563,05 41 194,1 1544,53
19 191,9 1562,23 42 194,2 ¡543,73
ПУБЛИКАЦИИ НА АНГЛИЙСКОМ ЯЗЫКЕ
Widespread use of DWDM systems has been made possible thanks to the development and production of a large number of various optical devices. Among them are the four main piece of equipment DWDM:
- optical terminal multiplexer (OTM-multiplexer);
- regenerator;
- optical amplifier;
- optical add / drop multiplexer (OADM-multiplexer).
The main components are the optical terminal multiplexer optical multiplexer (OM) and an optical demultiplexer (OD). In the transmit direction OM multiplexes (combines) the signals with fixed wavelengths in the baseband signal, which is transmitted via an optical cable. At the reception OD demultiplexes (separates) the baseband signal to signals with fixed wavelengths.
Optical regenerator is used to reshape the baseband signal and improve the signal / noise ratio. To this end, the baseband signal at the input of the regenerator is converted into an electrical form, the reduction is carried waveform, and further it is converted back to optical form.
The optical amplifier amplifies a baseband signal without recovering its shape. When transmitting data over long distances, amplifiers equipped with the equalizer function -
power leveling optical channels. In urban environments equalizer function is not used, and this reduces the cost of the amplifier. The optical amplifier is the cheapest piece of equipment DWDM (compared to the OTM-multiplexer and a regenerator).
In addition to the main components for optical communication systems at high technological level produced optical couplers (splitters), optical attenuators, optical connectors and other devices. Adjustment, repair and control equipment is carried out by a large number of measuring instruments, using modern computer technology.
In summary, it can be concluded that the combination of scientific advances optical communications and has revolutionized the modern system of information communications.
References
1. Custine A. Russia in 1839. Ed. House: "Zakharov" 2007.
2. Kalinin AI Propagation and operation of radio. M.: Svyaz'izdat, 1971).
3. Nyberg N.D. Theoretical basis of the color reproduction. M.: Soviet science, 1948.
ЭЛЕКТРОСВЯЗЬ И ОПТИКА В ИСТОРИЧЕСКОМ ПЛАНЕ Аджемов А.С., Хромой Б.П., МТУСИ, Москва, Россия
Аннотация
Широкое применение волоконно-оптических систем связи считается важным достижением науки и техники за последние десятилетия. При этом существует мнение, что в историческом аспекте это естественный процесс развития связи, поскольку на протяжении целого столетия человечество осваивало все более высокие частотные диапазоны радиоволн и, наконец, освоило оптический диапазон. В действительности история связи охватывает существенно больший промежуток времени и её начало связано с использованием оптического диапазона. Объединение научных достижений оптики и связи произвело революцию в современной системе инфокоммуникаций. В настоящее время волоконно-оптическая связь фактически становится определяющей в мире телекоммуникаций. Уже все континенты в мире связаны между собой волоконно-оптическими линиями связи. Без современной волоконно оптической связи в настоящее время не могла бы работать сеть интернет. Таким образом, спустя практически 150 лет связь снова стала оптической.
Представляет интерес технические характеристики компонентов ВОЛС, которые определяют возможности оптической сети. Безусловно, главным компонентом является оптическое волокно. Изобретение оптического волокна и его совершенствование, привело к созданию нового раздела оптики, называемым "волоконной оптикой".
Литература
1. Кюстин А. Россия в 1839 году Изд. дом: "Захаров", 2007.
2. Калинин А.И. Распространение радиоволн и работа радиолиний. М.: Связьиздат, 1971.
3. Нюберг Н.Д. Теоретические основы цветовой репродукции. М.: Советская наука, 1948.
